The document describes an eddy-current displacement sensor system for testing the vacuum integrity of sealed food containers in a fully automated process. The non-contact sensor scans the cap shape generated by the vacuum to calculate cap bending with high accuracy and compare it to a permissible value range to determine container quality. The eddy-current sensor is suitable for this application as it allows for a fully-automatic and non-contacting vacuum test that is well-adapted to the production process and can withstand environmental influences like moisture and temperature fluctuations.

1. A042_e
Eddy-current displacement sensors
eddyNCDT
Vacuum integrity of cans, jars, and bottles
After preserving jars are filled and closed they Technical details
must be vacuum-tested in fully automatic - Measuring range: 3 mm/6 mm
operation to immediately sort out any defective - Resolution: < 16 µm
containers. During transport of the jars an eddy- - 50 - 180000 pieces/hour
current sensor scans the cap shape that is
generated by the vacuum in a non-contacting way. Ambient conditions
The subsequent electronic unit calculates cap - Temperature: 20 - 80° C
bending, which directly depends on the internal - strong vapour,
pressure, with high accuracy. After comparing this - Very wet environment
value with a specified permissible value range a
decision is made about the quality of the internal System configuration
pressure and thus about the tightness of the - water proof sensor with 3 m cable
preserves container. - Light barrier to detect cans without lid or tilted
cans
Principle
Sensor Reasons for choosing the system
- Fully-automatic, non-contacting vacuum test
- Optimum adaptation to the production process
- Almost unlimited service life without system
C B A
disturbances
- Environmental influences such as moisture,
pungent vapours (vinegar) in the field of wet and
sticky food, and temperature fluctuations must
Direction
not influence the function of the system
- Counter for total throughput and for the number
of ejected glasses
Pic: Pano Verschluß GmbH, Itzehoe
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